Lightning location systems are known which include a number of cloud to ground lightning detectors separated by distances of tens to hundreds of miles. One known lightning detector provides azimuth and field amplitude information for each detected lightning discharge as well as the time of occurrence of the discharge as measured by the detector's clock. This data is sent from each of the detectors which have observed a lightning discharge to a central site or office where the location of the cloud to ground lightning discharge is determined. In order to calculate the location of a lightning discharge the data for a discharge observed by one detector must be correlated with the data for the same discharge observed by another detector. The clocks employed in known detectors typically drift and are not precise enough to enable the central office to correlate lightning data simply by matching the time of occurrence of a discharge as measured by one detector with the time of occurrence of a discharge as measured by a second detector. Clocks, such as atomic clocks having long term drifts of less than 1 millisecond would provide timing data with sufficient accuracy to correlate lightning based on time of occurrence alone. However these clocks are too expensive and impractical for the environments in which known lightning detectors operate.
In order to correlate lightning discharge data from two or more detectors, known lightning location systems have used dedicated communication lines for the transmission of data from each of the detectors to the central site, wherein the transmission delays for such lines are fixed and known. The central site of such known systems correlates the lightning discharge data based on the time of arrival of the data at the central site with a correction factor based on the transmission delay associated with the detector's communication line. A major disadvantage of such systems is the extremely high cost of the dedicated communication lines.